<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="[merchant_id]">
<input type="hidden" name="item_name" value="[item_name]">
<input type="hidden" name="amount" value="[amount]">
<input type="hidden" name="no_note" value="1">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="item_number" value="[item_number]">
<input type="hidden" name="custom" value="[user_id]">
<input type="hidden" name="return" value="[return]">
<input type="hidden" name="notify_url" value="[notify]">
<input type="image" src="[merchant_button]" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
</form>